I wish to search backwards from a given point in a large scalar using a regular expression. Using the <samp>pos</samp> function, and <samp>m//g</samp> I can set an arbitrary position in a scalar, and use <samp>m/\G.../g</samp> to search from the position forward. I want to search backwards from this point. Ideally, a construction like the following would work:
if($doc =~ /foo\G/g) { print "position preceeded by foo!\n"; }

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but perl requires that <samp>\G</samp> be placed only at the beginning of the regex.

One option is to make a substring of the document up to this position, and then just use <samp>$</samp> to mark the end. But this is a large document (all in one scalar) that will be matched this way many times, and string copying is expensive.

In reply to Backwards searching with regexps by Anonymous Monk

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